1. Field of the Invention
This invention relates to electrical connectors for coupling leads from a patient to a monitor for displaying signals appearing on the leads reflecting a condition of the patient. More particularly, the present invention relates to a disposable electrical connector for use with a pregnant patient in labor to couple the leads of a fetal scalp electrode to a remote monitor of the status of the fetal heart beat.
2. Background Art
During medical procedures it is frequently useful to monitor a condition of a patient through a display of electrical signals generated in the body of the patient which are reflective of the condition. To facilitate movement by and around the patient, it is generally desirable that electrical equipment associated with the monitor and the electrical equipment connected to the patient be selectively separable. Nevertheless, when actually utilized, these two components of the monitoring system must be readily and reliably interconnectable.
This is particularly true, for example, in fetal monitoring, which is now commonplace. Electrical signals generated in the fetus are a reliable indicator of the fetal heart beat, which in turn is useful to medical practitioners in detecting fetal distress and in gauging fetal health.
Although useful in other circumstances, the technique of fetal monitoring has and continues to be employed primarily during the time that a pregnant patient is in labor. Typically, one or more electrodes is attached to the scalp of the fetus and then connected by way of leads passing through the birth canal to an electrical monitoring device. Commonly the electrodes take the form of pointed wires bent into a helical shape at the tip of a probe that is inserted through the birth canal into contact with the fetal scalp. Rotation of the probe causes the leads to catch and become embedded in the tissue of the fetal scalp.
In the past it has almost uniformly been the case that a reference electrode is attached directly to the body of the pregnant patient in order to establish a base or reference voltage for use in calibrating and stabilizing the monitor display. This reference electrode has taken a number of forms. Initially a metal plate was wired directly to the monitor and secured using tape in direct contact with the skin of the patient. A conductive gel was used between the plate and the skin of the patient to enhance the electrical contact.
Alternatively, the reference voltage plate was incorporated into an electrical connector which also served to selectively couple the leads from the fetal scalp electrode with a cable connected to the electronic monitor. It was necessary that this type of electrical connector effect secure mechanical and electrical interconnections between the leads from the fetal monitor and corresponding signal conductors in the cable attached to the monitor. In addition, by placing the reference voltage plate of the connector in appropriate contact with the skin of the pregnant patient, the connector developed a reference voltage which in turn was couplable to a reference connector in the cable.
Such electrical connectors were routinely held in place against the abdomen or the thigh of the patient by a belt or strap. Effective electrical contact between the reference voltage plate and the skin of the patient continued to be facilitated through use of a conductive gel. When thusly mounted to the body of a patient, however, the electrical connector exhibited a capacity to migrate away from the site at which the conductive gel had been applied. In addition, the belt or strap by which the connector was held in place came to be perceived as an uncomfortable encumbrance upon the freedom of the patient to move during labor.
Accordingly, an alternative manner of effecting the required reference voltage contact and of holding the connector in place was developed. This involved a disposable adhesive patch which was applied to the skin of the patient. The side of the adhesive pad in contact with the patient was provided with a recess or a pad containing electrically conductive gel. This reservoir of gel was electrically coupled to a male metallic snap fitting on the opposite of the patch. Once applied to the skin of the patient, the adhesive patch provided a site for obtaining the desired reference voltage which would not migrate. The electrical connector was correspondingly provided on the side to be placed in contact with the patient with a female snap fitting recess.
In this way, the electrical connector was mechanically attached to the adhesive pad, preventing its migration. Through electrical conductors located in the cooperating snap fittings, the electrical connector could also reliably couple a reference voltage to the same cable as was used to transmit signals from the fetal electrode to the electronic monitor.
Recent experience and advancement of electronic monitors has lead many practitioners to forego what was formerly a mandatory reliance on the reference voltage. Thus, while some medical personnel continue to use a conductive gel and a reference voltage plate or an adhesive pad and snap, others are content either to use the reference plate without a gel or to forego any reference voltage whatsoever.
While the electrical connectors described above exhibit advances in terms of convenience and reliability over the earliest forms of connectors and reference plates employed in this setting, they are afflicted by a number of disadvantages.
Firstly, such electrical connectors continue to exhibit undesireable mechanical complexity by utilizing a large number of distinct components. For example, most employ one or another form of spring biased clips with which to effect electrical contact with the leads of the fetal scalp electrode. A spring biased approach to this function necessitates at least two components which slide in relation to each other and one or another form of a spring for biasing these into a position which clasps each lead from the fetal electrode. These components are not only distinct from the connector body, requiring mechanical attachment thereto, but must in addition be coupled to electrical wiring therewithin.
Such structural realities are in turn reflected in complex manufacturing procedures and high costs of production. Expense has necessitated that the electrical connectors be reusable, imposing on hospitals the cost of purchasing and maintaining an inventory. Expense is not, however, the only difficulty encountered in known electrical connectors for use in this environment.
Due to the complexity of their construction many electrical connectors are heavy and bulky. This results in their inhibiting patient freedom and in their being difficult to secure at a fixed location. It has been found that spring loaded clips, despite their mechanical complexity, are difficult to couple and uncouple with the appropriate fetal electrode leads. Where miniaturization efforts are undertaken in order to reduce bulkiness and to gain some cost advantage, complex clipping systems become even more difficult to operate.
Thus, the goal of small size runs in some respects counter to that of convenient operation. One factor is traded off for the other, without significantly improving the overall device.
Practitioners are currently divided over the manner in which it is preferred to establish an electrical reference voltage. Electrical connectors adapted for one mode of use are also capable of functioning in the other. Thus, medical personnel must adopt both an electrical connector and a means for obtaining a reference voltage which are in harmony. This limits flexibility. Those practitioners who feel free not to rely on a reference voltage do not appreciate the extra cost occasioned in such electrical connectors by the provision of reference voltage plates or other structures for that purpose.
Thus, in relation to electrical connectors for use in systems employing fetal scalp electrodes, the goals of miniaturization, disposability, versatility, and ease of operation are to various extents in conflict one with another. As a result, an optimum combination has yet to be developed.